Influence of photoresist layer on unetched guided mode resonance filter

Abstract

During guided mode resonance (GMR) filter fabrication by ion beam etching in a vacuum chamber, the most difficult aspect of the process is accurate control of the groove depth. Because the resonant wavelength of the GMR filter is susceptible to variations in the fabrication parameters, such as the groove depth and period of the grating, it is very difficult to fabricate an ideal GMR filter that has the same parameters as the designed filter. Therefore, to simplify this fabrication process, a GMR filter that can be fabricated without etching is presented in this paper. However, the proposed filter will bring new problems in that the lack of etching may lead to the presence of a residual photoresist layer during the holographic interferometry process. In this paper, we focus on the influence of the residual photoresist layer on the unetched GMR filter. The effects of different photoresist layer thicknesses and different development times are investigated. Using numerical methods based on rigorous coupled wave analysis (RCWA), the spectral curve shows a blue shift with increasing development time. Moreover, with a constant development time and exposure time, there is a red shift with the increase of the photoresist layer thickness. It is found experimentally that this spectral shift trend agrees well with the results of the theoretical analysis.